This patent specification relates to a power supply method and apparatus, and more particularly to a power supply method and apparatus that effectively reduces power consumption.
Conventionally, a power supply apparatus that reduces a direct current supplied from a direct current power source (e.g., a battery) to a predetermined voltage is classified into two types; one type using a voltage regulator and the other type using a DC-to-DC converter.
FIG. 1 shows an exemplary circuit of a background power supply apparatus using a voltage regulator 100. In the voltage regulator 100 of FIG. 1, a P-channel-type MOS (metal oxide semiconductor) transistor 102 (hereinafter referred to as a P-MOS transistor 102) and resisters 103 and 104 are connected in series between a power source terminal applied with a power source voltage VDD by a direct current 101 (e.g., a battery including a secondary battery) and ground. The resisters 103 and 104 divide a voltage Vout which is compared by a voltage comparator 106 with a predetermined reference voltage Vref generated by a reference voltage generator 105. Based on a comparison result, an operation of the P-MOS transistor 102 is controlled so that the voltage Vout is held at a desired value. In FIG. 1, a CPU 107 is an exemplary system that requires power from the voltage regulator 100.
However, the above-described voltage regulator has a drawback that the P-MOS transistor 101 consumes a great amount of electric power for a reduction of the power source voltage VDD to the voltage Vout. More specifically, when the CPU 107 consumes a current of 100 mA, for example, and a voltage regulator 100 reduces the power source voltage VDD from 3.6 volts, for example, to 2 volts, for example, the P-MOS transistor 101 consumes the power of 0.16 W. That is, the voltage regulator consumes a difference of the battery voltage and the CPU""s operational voltage. Such voltage regulator is undesirable for a system aiming a low power consumption since the CPU""s operational voltage has been lowered in the recent years.
Accordingly, as shown in FIG. 2, a DC-to-DC converter is used in place of the voltage regulator as a power supply in a system (e.g., the CPU 107) using a battery. In FIG. 2, a DC-to-DC converter 110 reduces the power source voltage VDD to a predetermined voltage Vout and supplies the voltage Vout to the CPU 107.
In general, a system using a battery as a source of power is provided with a sleep function or temporarily stopping the operations of the system to reduce an electrical power consumption on an as needed basis. In the case of the power supply apparatus of FIG. 2, it is attempted to reduce the power consumption by changing the output terminal of the DC-to-DC converter 110 to the CPU 107 in the sleep mode from a ground level to a high impedance level. This is because the DC-to-DC converter 110 is used as an apparatus that directly controls the power source required by the system (e.g., the CPU 107).
On the other hands, the DC-to-DC converter 110 is required to be always in an active state in the case the system (e.g., the CPU 107) in the sleep mode is intermittently activated to control certain components on an as needed basis. In such a case, the power consumption by the DC-to-DC converter 110 shares a large part of the total system power consumption.
This patent specification describes a novel power supply apparatus. In one example, this novel power supply apparatus includes a DC-to-DC converted and a voltage regulator. The DC-to-DC converter is arranged and configured to perform a voltage conversion for converting a voltage of a power source supplied from a direct current power source to a first predetermined voltage. The first predetermined voltage is lower than the voltage of the power source. The voltage regulator is arranged and configured to carrying out a voltage regulation for regulating the first predetermined voltage of the power source to at least a second predetermined voltage. The second predetermined voltage is lower than the first predetermined voltage.
The DC-to-DC converter may be turned into a non-active state to stop the voltage conversion and straight passes the voltage of the power source when an operation mode is changed to a sleep mode.
The DC-to-DC converter may include a switching circuit, a smoothing circuit, and a controller. The switching circuit is arranged and configured to perform a switching operation for switching the power source and to output a pulsating current voltage. The smoothing circuit is arranged and configured to smooth the pulsating current voltage output by the switching circuit and to output a smoothed voltage to the voltage regulator. The controller is arranged and configured to detect the smoothed voltage output from the smoothing circuit and to control the switching circuit to change a performance of the switching operation in response to a detection result of the smoothed voltage so that the smoothed voltage output by the smoothing circuit is substantially equal to the first predetermined voltage. The controller is turned into a non-active state to cause the switching circuit to stop the switching operation so as to pass the voltage of the power source through the switching circuit and to output the voltage of the power source to the smoothing circuit when the operation mode is changed to the sleep mode.
The DC-to-DC converter may output the voltage of the power source without performing the voltage conversion when the operation mode is changed to the sleep mode.
The converter may include a switching circuit, a smoothing circuit, and a controller. The switching circuit is arranged and configured to perform a switching operation for switching the power source and outputting a pulsating current voltage. The smoothing circuit is arranged and configured to smooth the pulsating current voltage output from the circuit and to output a smoothed voltage to the voltage regulator. The controller is arranged and configured to detect the smoothed voltage output from the smoothing circuit and to control the switching circuit to change a performance of the switching operation in response to a detection result of the smoothed voltage so that the smoothed voltage output from the smoothing circuit is substantially equal to the first predetermined voltage. The controller causes the switching circuit to stop the switching operation so as to pass the voltage of the power source through the switching circuit and to output the voltage of the power source to the smoothing circuit when the operation mode is changed to the sleep mode.
The controller may connect a load to an output terminal of the smoothing circuit and controls a current flowing the load so as to reduce the voltage output from the smoothing circuit to the first predetermined voltage when the voltage output from the smoothing circuit is lower than the first predetermined voltage and when the operation mode is changed to a normal operation mode.
The controller may include a transistor, a comparator, and a current control circuit. The transistor operates as the load. The comparator performs a first comparison for comparing the voltage output from the smoothing circuit with the first predetermined voltage when the operation mode is changed to the normal operation mode and outputs a first comparison result. The current control circuit is arranged and configured to control the transistor to produce a current flowing therethrough in response to the first comparison result of the comparator when the operation mode is changed to the normal operation mode.
The current control circuit may control the transistor to increase the current at a first predetermined pace when the voltage output from the smoothing circuit is determined as greater than the first predetermined voltage based on the first comparison result performed by the comparator.
The current control circuit may control the transistor to continue to increase the current at the first predetermined pace for a first predetermined time period when the voltage output from the smoothing circuit is determined as substantially equal to the first predetermined voltage based on the first comparison result performed by the comparator. The current control circuit may further control the transistor to produce a saturated current flowing therethrough for a second predetermined time period immediately after the first predetermined time period.
The current control circuit may control the transistor to decrease the current at a second predetermined pace for a third predetermined time period immediately after the second predetermined time period.
The controller may detect a current output from the switching circuit and controls the switching circuit to vary the current in response to the detected current when the operation mode is changed to the sleep mode.
The controller may control the switching circuit to straight output the voltage of the power source to the smoothing circuit when the current detected is smaller than a predetermined value and to reduce the current output therefrom to a value smaller than the predetermined value in a predetermined manner when the current is greater than the predetermined value.
The controller may perform a second comparison between a reference voltage dropping at a substantially constant pace and the voltage output from the smoothing circuit in response to the detected voltage when the operation mode is changed to the normal operation mode, and controls a duty cycle of the switching operation performed by the switching circuit according to a result of the second comparison during a time the voltage output from the smoothing circuit is reduced to the first predetermined voltage.
The controller may perform a third comparison between another predetermined reference voltage and the voltage output from the smoothing circuit in response to the detected voltage, and controls a duty cycle of the switching operation performed by the switching circuit according to a result of the third comparison when the voltage output from the smoothing circuit is reduced to the first predetermined voltage.
This patent specification further describes a novel method of power supply. In one example, this novel method includes the steps of performing and regulating. The performing step performs a DC-to-DC conversion with a DC-to-DC converter to achieve a voltage conversion for converting a voltage of a power source supplied from a direct current power source to a first predetermined voltage. The first predetermined voltage is lower than the voltage of the power source. The regulating step regulates the first predetermined voltage of the power source to at least a second predetermined voltage. The second predetermined voltage is lower than the first predetermined voltage.
The performing step may turn the DC-to-DC converter into a non-active state to stop the DC-to-DC conversion and straight passes the voltage of the power source through the DC-to-DC converter to the voltage regulator when an operation mode is changed to a sleep mode.
The performing step may include the steps of executing, smoothing, detecting, changing, and stopping. The executing step executes a switching operation for switching the power source to output a pulsating current voltage. The smoothing step smoothes the pulsating current voltage output by the switching circuit to output a smoothed voltage to the voltage regulator. The detecting step detects the smoothed voltage output in the smoothing step. The changing step changes a performance of the switching operation in response to a detection result of the smoothed voltage so that the smoothed voltage output in the smoothing step is substantially equal to the first predetermined voltage. The stopping step stops the switching operation when the operation mode is changed to the sleep mode so as to apply the voltage of the power source to the smoothing circuit.
The DC-to-DC converted may output the voltage of the power source without performing the voltage conversion when the operation mode is changed to the sleep mode.
The performing step may include the steps of executing, smoothing, detecting, changing, and stopping. The executing step executes a switching operation for switching the power source to output a pulsating current voltage. The smoothing step smoothes the pulsating current voltage output in the switching step to output a smoothed voltage to the voltage regulator. The detecting step detects the smoothed voltage output in the smoothing step. The changing step changes a performance of the switching operation in response to a detection result of the smoothed voltage so that the smoothed voltage output in the smoothing step is substantially equal to the first predetermined voltage. The stopping step stops the switching operation when the operation mode is changed to the sleep mode so as to apply the voltage of the power source to the smoothing circuit.
The above-mentioned novel method may further includes steps of providing, applying, and adjusting. The providing step provides a transistor as a load. The applying step applies the voltage output in the smoothing step to the transistor so that a current flows through the transistor when the voltage output in the smoothing step is lower than the first predetermined voltage and when the operation mode is changed to a normal operation mode. The adjusting step adjusts the current flowing the load so as to reduce the voltage output in the smoothing step to the first predetermined voltage.
The adjusting step may include the steps of performing and causing. The performing step performs a first comparison for comparing the voltage output in the smoothing step with the first predetermined voltage when the operation mode is changed to the normal operation mode to output a first comparison result. The causing step causes the transistor to produce a current flowing therethrough in response to the first comparison result of the comparing step when the operation mode is changed to the normal operation mode.
The causing step may cause the transistor to increase the current at a first predetermined pace when the voltage output in the smoothing step is determined as greater than the first predetermined voltage based on the first comparison result performed in the comparing step.
The causing step may cause the transistor to continue to increase the current at the first predetermined pace for a first predetermined time period when the voltage output in the smoothing step is determined as substantially equal to the first predetermined voltage based on the first comparison result performed in the comparing step, and may cause the transistor to produce a saturated current flowing therethrough for a second predetermined time period immediately after the first predetermined time period.
The causing step may cause the transistor to decrease the current at a second predetermined pace for a third predetermined time period immediately after the second predetermined time period.
The above-mentioned method may further include the steps of detecting and instructing. The detecting step detect a current output in the switching step when the operation mode is changed to the sleep mode. The instructing step instruct the switching step to change the current in response to the detected current.
The instructing step may instruct the switching step to straight output the voltage of the power source to the smoothing step when the current detected is smaller than a predetermined value and to reduce the current output in the switching step to a value smaller than the predetermined value in a predetermined manner when the current is greater than the predetermined value.
The novel method may further include the steps of performing and determining. The performing step performs a second comparison between a reference voltage dropping at a substantially constant pace and the voltage output in the smoothing step in response to the detected voltage during a time the voltage output in the smoothing step is reduced to the first predetermined voltage. The determining step determines a duty cycle of the switching operation performed in the switching step according to a result of the second comparison.
The above-mentioned novel method may further include the steps of performing and controlling. The performing step performs a third comparison between another predetermined reference voltage and the voltage output in the smoothing circuit in response to the detected voltage. The controlling step controls the duty cycle of the switching operation performed in the switching step according to a result of the third comparison when the voltage output in the smoothing step is reduced to the first predetermined voltage.